Michael Montgomery is accused of homicide in the stabbing death of Jonathan Denver following a Giants-Dodgers game on September 25, 2013. (Facebook / CBS)Michael Montgomery is accused of homicide in the stabbing death of Jonathan Denver following a Giants-Dodgers game on September 25, 2013. (Facebook / CBS)

District Attorney George Gascon said Friday he has asked police for additional evidence in the case before he decides whether to file charges against Michael Montgomery of Lodi in the fatal stabbing of 24-year-old Jonathan Denver.

Police provided the district attorney’s office with the results of an initial investigation Friday, but Gascon said not all witnesses have been interviewed. In particular, he noted that there were no interviews with independent witnesses.

Gascon said prosecutors need to be certain they can prove a case beyond a reasonable doubt before proceeding.

Jonathan Denver (Mendocino County Sheriff’s Office)

“Additionally, in California, it is the People’s burden to prove beyond a reasonable doubt that the defendant did not act in lawful self-defense,” Gascon said. “It is vital for our office to have independent corroboration of the incident in order to meet our ethical obligation to charge this case.”

Montgomery was arrested Wednesday on suspicion of fatally stabbing Denver around 11:35 p.m. that evening near Third and Harrison streets.

Denver, who was wearing Dodgers clothing and whose father was a security guard for the team, was apparently stabbed after an argument related to the rivalry between the Dodgers and Giants, San Francisco police Chief Greg Suhr said on Thursday.

He had been watching the Giants-Dodgers game with his father, brother and two others earlier in the evening but had left in the eighth inning to go to a bar.

“My office extends its deepest and most heartfelt condolences to Jonathan Denver’s family,” Gascon said. “We are extremely concerned about the loss of life and want to make sure justice is served.”

Gascon described ballpark security and fan violence as matters of great concern to him.

“We have great sports venues and we’ll do everything we can to make them safe,” he said.

The death of Denver, who worked as a plumber’s apprentice for North Coast Plumbing, Heating & Sheet Metal Inc. in Fort Bragg, is the latest violent incident to mar the Giants-Dodgers rivalry.

In 2011, Giants fan Bryan Stow was beaten after the team’s season opener at Dodger Stadium in Los Angeles, and suffered severe brain injuries. Two people have been charged in that beating and are awaiting trial.

Gascon said that anyone with video of the incidents leading up to Wednesday night’s stabbing should contact police immediately.

(Copyright 2013 by CBS San Francisco and Bay City News Service. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.)